Electric valve converting system



March 19, 1940.

A. H. MITTAG 2,193,933

ELEGQRIG VALVE CONVERTING SYSTEM Original Filed Feb. 17, 1938 3 Sheets-Sheet l Irwverwtor: Albert H. Mittag H is Attorn 2y.

March 19, 1940. A. H. MITT AG 2,193,933

'ELECTRIC VALVE CONVERTING SYSTEM Original Filed Feb. 17, 1938 3 Sheets-Sheet 2 L: L:| a 3 2 w W m O u w w Em mu 6 M .G n m i N F RS w hw March 19, 1940. A. H. MITTAG 2,193,933

ELECTRIC VALVE CONVERTING SYSTEM Original Filed Feb. 17, 1938 s Sheets-Sheet 5 Fig.4.

Inventor:

b x :XYMZM jHi fittobney.

Albert H. Mittag,

Patented Mar. 19, 1940 UNITED STATES PATENT OFFICE Albert R. Mittll; Schenectady, N." Y., assignor to General Electric Company, a corporation of New York Original application February 17, 1938, Serial No.

Divided and this application November 30, 1938, Serial No. 243,176

' Claims.

My invention relates to electric valve' converting systems and more particularly to such systems suitable for transmitting energy between alternating current circuits of different frequencies.

This application is a division of my copending application Serial No. 191,046, filed February 17,

I 1938, entitled Electric valve converting system,

and assigned to the assignee of the present application.

Heretofore numerous electric valveconverting systems have been utilized for the transfer of energy between alternating current circuits of different frequencies and numerous arrangements have been proposed for controlling electric valve converting systems in accordance with the voltage and current conditions of the output circuit. Such arrangements, however, in many instances have involved complicated auxiliary apparatus and obviously it is desirable to obtain a system in which such control could be obtained with a minimum amount of auxiliary apparatus. Where such electric valve converting systems have been utilized to control the speed of a motor or dynamo-electric machine it is desirable to obtain a relatively flat load speed characteristic and this may be obtained by controlling the converter in accordance with the voltage and current conditions of the motor. In accordance with my invention I compensate for the field distortion of the machine as the load increases by advancing the moments of ignition oi the valves of the converter thereby obtaining a relatively flat speed torque characteristic of the motor.

It is therefore an object of my invention to provide an improved electric valve converting system utilizing a minimum of auxiliary apparatus.

It is a still further object of my invention to provide an improved electric valve converting system for transferring energy between alternating current circuits of difierent frequencies in which the apparatus is controlled in accordance with the voltage and current conditions of the output circuit.

It is a still further object of my invention to provide an improved electric valve converting system for transferring energy between an alternating current circuit and a dynamo-electric machine in which the moments of ignition of the electric valves are advanced in accordance with increasing load upon the motor or dynamo electric machine.

The novel features which are believed to be characteristic of this invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, will be bet- 5 ter understood by reference to the following description taken in connection with the accompanying drawings in which Fig. 1 represents one embodiment of my invention wherein an electric valve converting system supplies energy to 10 an alternating current machine of the synchronous type; Figs. 2 and 3 are explanatory of the operation of my invention; Fig. 4 is a further modification of my invention in which an electric valve converting system supplies energy to an 15 alternating current machine of the synchronous type; and Fig. 5 shows how my invention may be utilized in connection with an electric valve converting system for transmitting energy between two different alternating current circuits. 20

Referring now more particularly to Fig. 1 of the drawings, there is illustrated an arrangement embodying my invention for transferring energy between a polyphase alternating current circuit l0 and a synchronous alternating current 25 motor II. A dynamo-electric machine or motor II has been shown as comprising a plurality of phase windings I2, 13 and I 4, and a rotatable field winding IS. The rotatable field winding l5 may be supplied by any'suitable source of direct 30 current or may be energized from a rectifier apparatus comprising a pair of valves 16 and i1 and an inductive winding l8. This winding i8 is energized from one phase of the alternating current circuit Ill. The electric valve converting ap- 5 paratus utilizes six groups of three tubes each, i9, 20, 2|; 22', 23, 24; 25, 26, 21; 28, 29, 39; 3|, 32, 33; and 34, 35, 36. The cathodes of the valves i9, 22 and 25 and the anodes of the valves 28, 3| and 34 are connected through an inductive 4o winding 31 to one of the conductors of the alternating current circuit Ill. The cathodes of the valves 20, 23 and 26 and the anodes of the valves 29, 32 and 35 are connected through another inductive winding 38 to one of the other 45 conductors of the polyphase alternating current circuit l0, and similarly the cathodes of the valves 2|, 24, and 21 and the anodes of the valves 30, 33 and 36 are connected through an inductive winding 39 to the remaining conductor of 50 the polyphase alternating current circuit Ill. The anodes of the group of valves I9, 20, 2| and the cathodes of the group of valves 28 29, 30 are connected to the phase winding I4 of the motor H.

the cathodes of the group of valves 36, $32, 323 are connected to the phase winding l3 oi the electric motor and the anodes of the group of valves 25, 26, 211 and the cathodes of the group of valves 34, 35, 36 are connected to the phase winding 62 of the electric motor.

In order to control the conductivities of the several electric valves that supply current succes sively to the several phase windings of the synchronous machine H, the control electrodes or grids of the several groups of electric valves are adapted to be selectively excited by means of a distributor 49 which is mounted on the shaft of the machine II and six auxiliary electric valves one of which is shown as valve 4|. The distributor 40 is provided with six brushes each of which is connected to a valve similar to valve 4|. The valve 4| and each valve similar thereto controls three control transformers for a group of valves much as'valves i9, 29, 2t. Alternating current obtained from the source i9 is transmitted through a suitable phase shifting device such as 42 to a transformer having primary winding 43 and secondary winding 44. Three of the phase windings of the secondary winding 44 are connected to the control transformers 45, 46, 41, respectively and these transformers are connected through unilaterally conductive devices of contact rectiflers 48, 49, 50, respectively, tothe anode of the auxiliary valve 4|, the cathode of which is connected to one of the brushes of the distributor 40, the distributor segment of which in turn is connected to the neutral point of the phase windings of. the secondary winding group 44. Each of the control circuits for the valves may include a suitable source of biasing potential (not shown) and a current limiting resistor. The auxiliary valve 4| is provided with a control circuit which is responsive to the voltage and current condition of the phase winding of the synchronous machine II. The transformer 5I is provided with primary windings which are connected so as to be energized in accordance with the voltage appearing across the terminals of the phase windings I2, I3, I4 of the synchronous machine II. The secondary windings of the transformer 5| are six in number corresponding to the number of auxiliary valves similar to valve 4|. Two current transformers 52 and 53 are connected to the conductor supplying energy to the phase winding I4 of the motor and current transformers 54, 55 and 56, 51 respectively are connected to the conductor supplying energy to the phase windings I3 and I2 of the machine II. One ofthese current transformer windings 52 is connected in series with one of the secondary windings of the transformer 5| in the control circuit for the electric valve 4| which includes the resistors 58 and 59. The electric valve 4| is therefore rendered conductive in accordance with the voltage and current conditions appearing across the phase windings of the synchronous motor II. The distributor 40 serves to select which group of valves may be rendered conductive, the auxiliary valve such as 4| determines the instant at which one of the valves of that group will be rendered conductive, and the phase relation between the alternating current circuit I9 and the voltage supplied to the control transformers such as 45, 46 and 51 will determine which one of. the valves of the group will be rendered conductive. For purposes of simplicity in disclosure the control circuits for these various valves have been shown as applied to only one group of valves comprising the valves I9, 20, 2|.

it therefore will be apparent to those skilled in the art that six circuits similar to those shown in the drawings are necessary in order to provide a complete control circuit for all of the electric valves. A switch 69 is provided for each of the valves similar to valve 451 which is closed momen tarily in order to start the motor and as soon as the motor begins to move the switch 6!! and corresponding switches are simultaneously opened and the apparatus then begins to function in a manner which will be apparent to those skilled in the art.

In explaining the operation of the above-described apparatus, it will be assumed that initially the rotary phase shifting device 42 is so adjusted that the alternating potential impressed upon the several grid controlled circuits is retarded substantially with respect to the potential of the alternating current circuit I0 and that the rotatable field winding I5 and the distributor 40 are in approximately the positions illustrated. It further will be assumed that just prior to the positions illustrated current was conducted from the line I0 by the group of valves 3|, 32, 33

through phase winding I3, phase winding I2 and through the group of valves 25, 26, 21 to the other side of the alternating current circuit I9. In the position shown in the drawings current is now being conducted by the group of valves 3 I, 32, 33 through phase winding I3, phase winding I4 and the group of valves I9, 20, 2|. winding I5 progresses still further current will be conducted by the group of valves 34, 35, 36 through phase winding I 2, phase winding I4, and through the group of valves I9, 20, 2|. Upon further advance of the field winding the conductivity will be as follows: From a group of valves 34, 35, 36 through phase winding I2, phase winding I3 and group of valves 22, 23, 24. From the group of. valves 28, 29, 30 through phase winding I4, phase winding I3 and the group of valves 22, 23, 24. This will be followed by conduction of current by the group of valves 28, 29, 30 through phase winding I4, phase winding I2, and the group of valves 25, 26, 21. Thereafter the cycle of operation just described will be repeated.

If the valve 4| were not interposed between the distributor 40 and the various control transformers such as 45, 46 and 41, the main valves I9 to 36, inclusive, would fire at the instant B commutating voltage shown as D and furthermore there would be a reduction in speed of the motor I I. The introduction of the auxiliary valve such as 4| causes the motor to operate at the point B at light load and to advance the moment of ignition to point A at heavy load. This advancement of the point of ignition to point A as shown in Fig. 2 will provide a relatively flat speed torque characteristic. This advancement of the moment of ignition of the main valves I9 to 36 from point B to point A under dlfierent load conditions is accomplished by the introduction of the control impulse obtained from the current transformer 52 in the control circuit of the auxiliary valve 4|. Fig. 3 shows the relation of the various voltages supplied to the control circuit of the auxiliary valve 4|. Thus the voltage Em represents the voltage ob tained from one of the secondary windings of the transformer 5I and the voltage El represents the voltage component derived from the current As the field transformer such as 82. Thus the resultant control voltage is shown as E which has been advanced in position by an angle equal to a. Obviously as the current flowing through the phase windings of the motor increases due to increased load the componentEi will become greater thereby advancing the moment of ignition of the main valves such as I8 to 88.

While I have shown a single auxiliary valve such as 8| connected in series with each of the various brushes of the distributor 88, of course it will be apparent to those skilled in the art that a similar result could be obtained by the utilization of three auxiliary valves which would supplant the auxiliary valve 8| and the contact rectifiers or unilaterally conductive devices 88, 88 and 88.

In Fig. 4 there is shown an arrangement for transmitting current from the alternating current source 8| to a series excited synchronous type dynamo-electric machine 82. A plurality of reactors 88, 88, 88 are connected between the alternating current source 8| and the various electric valves of the converting apparatus. Six groups of three valves each are provided, 88, 81, 88; 88, 18, II; 12, 18, 18; 18, 18, 11; 18, 18, 88; and 8|, 82, 88. The cathodes of the valves 88, 88, 12 and the anodes of the valves l8, 18, 8| are connected together to one of the conductors of the polyphase alternating current circuit 8|. The cathodes of the valves 81, I8, 18 and the anodes of the valves 18, 18, 82 are all connected to another one of theconductors of the alternating current supply circuit. Similarly the cathodes of the valves 88, 1|, 18 and the anodes of the valves 11, 88, 88 are connected to the remaining conductor of the alternating current circuit 8 I. The dynamo-electric machine or motor 82 is provided with two groups of phase windings 88, 85, 88 and 81, 88, 88 and a rotatable field winding 88. The anodes of the group of valves 88, 81, 88 are connected together to one terminal of the phase winding 88; the anodes of the valves 88, 18, 1| are connected to one terminal of the phase winding 88, while the anodes of the valves 12, 18, 18 are connected to one terminal of the phase winding 81. The cathodes of the valves 18, 18, 11 are connected to one terminal of the phase winding 88; the cathodes oi the valves 18, 18, 88 areconnected to one terminal of the phase winding 88 and the cathodes of the valves 8|, 82, 88 are connected to one terminal of the phase winding 88. The neutral point of the phase windings 88, 88, 88 is connected to one terminal of the rotatable field winding 88 and the other terminal of the field winding is connected to the neutral point of the phase winding group 81, 88, 88. Thus it is apparent that the synchronous motor shown is of the series excited type. The flow of current through the various phase winding groups comprises unidirectional current impulses so that the current flow through the rotatable field winding 88 is substantially of direct current nature.

The electric valves 88 to 88 are controlled by a control circuit which includes a distributor 8| mounted on the shaft of the machine 82 and a plurality of auxiliary electric valves such as 82. Six valves similar to valve 82 are provided,

one for each of the brushes of the distributor 8|, and each oi these valves controls the energization of one of the six groups of main valves by means of three control transformers 88, 88. 88 and three unilaterally conductive devices 88,

81, 88. Each of the primary windings of the three transformers 88, 88, 88 is connected in series with'one of the phase windings 88 of the transformer I88, the primary winding |8| 'of which is connected to be energized through a suitable phase shifting device I82 from the alternating current source 8|. The transformer I88 may be provided with six groups of secondary windings similar to the groups 88, each group serving one or the other of the electric valves similar to the valve 82. Each of the conductors leading to the various phase windings 88, 88, 81, 88, 8'8, 88 of the synchronous motor 82 is provided with a current transformer I88, I88, I88, I88, I81, I88, respectively, one of which is included in the control circuit for the auxiliary. valves such as valve 82. The control circuit for the valve 82 therefore includes one of the current transformers such as I88 and one of the secondary windings of the transformer I88 the primary winding of which is connected across the terminals of one of the phase groups of the synchronous motor 82 such as the phase group 88, 88, 88. Thus the electric valve 82 is rendered conductive in accordance with the voltage and current conditions of the phase windings of the synchronous machine 82. The valves 88 to 88 are therefore controlled in a manner similar to the control of the valves shown and described in connection with Fig. 1, that is, under light load conditions the moment of ignition of the main valve is primarily determined by the voltage component supplied by the secondary winding of the transformer I88 and as the-load increases on the motor the voltage component supplied I by the current transformer I 88 serves 'to advance the angle of the moment of ignition of the valve 82 with a corresponding advance in the moments of ignition of the valve controlled by the auxiliary valve. For the purpose of starting the converting apparatus a suitable switch such as switch 925, is provided for each of the auxiliary valves corresponding to valve 82, and this is closed only during the starting operation after which it is opened. K

The arrangement shown in Fig. 5 is suitable for transferring alternating current from a source of alternating current 8 to an alternating current load circuit III which may be of a different frequency or the same frequency having a different phase relation relative to the potential appearing across the polyphase circuit II8. This apparatus comprises six groups of three tubes each, H2, H8, H8; H8, H8, Ill; H8, H8, I28; I2I, I22, I28; I28, I28, I28; and I21, I28, I28. The cathodes of the valves H2, H8 and 8' are connected to one terminal of the inductor I88 and the anodes of the valves I2I, I28 and I21 are connected to the other terminal of the inductor I88 the midpoint of which is connected to one of the conductors of the polyphase alternating current circuit 8. Similarly the cathodes oi the valves H8, H8, and 8 are connected to one terminal of the inductor |8I and the anodes of the valves I22, I28 and I28 are connected to the other terminal of this same inductor the midpoint of which is connected to one of the conductors of the circuit H8. The cathodes of the valves II8, III, and I28 are connected-to one terminal of the inductor I82 while the anodes of the valves I28, I 28 and I28 are connected to the other terminal 01' this inductor the midpoint of which is connected to one of the other conductors of the supply circuit H8. The

valves I 2|, I22 and I23 to one of the conductors of the alternating current output or load circuit III. Similarly the anodes of the valves H5, H5, II 1 and the cathodes of the valves I24, I25, I26 are connected together to one of the other conductors of the output or load circuit I I I. The anodes of the valves II 8, H9, I20 together with the cathodes of the valves I21, I23, I28 are connected together to the remaining conductor of the output circuit I I I.

The various valves of the system are controlled by a circuit which includes a suitable phase shifting device I33 energized from the source of alternating current II 0 and which device supplies energy to the primary winding I34 of a transformer the secondary windings I35 of which are arranged to be connected in series with the various control transformers of the individual valves. The secondary windings I35 are arranged in star relation and three of these windings are connected in series with the control transformers I38, I31 and I38 which transformers are connected through the unilaterally conductive devices I39, I40 and HI, respectively to the anode of one of a plurality of auxiliary valves such as valve I 42. The cathode of valve I42 is connected to one of the brushes of a distributor I43 the rotating segment of which is connected to the neutral point of the transformer secondary winding group I36. The distributor I 43 is driven by a synchronous motor I44 the various phase windings of which are energized from the output circuit III through a transformer I45. The field winding of the motor I44 may be energized from any suitable source of direct current such as the battery I46 or a rectifier supplied from one phase of the alternating current circuit IIIl.- Since the synchronous machine I44 operates at a speed corresponding to the frequency of the output circuit III, the distributor I43 will cause the various valves II2 to I29 to be rendered conductive in the proper sequence. These various valves, however, cannot be rendered conductive until the valve I42 is rendered conductive. This valve is provided with a control circuit which includes one of the current transformer windings I41 and one of the secondary windings of the transformer I48. For the purposes of simplicity only one auxiliary valve I42 has been shown, although six valves are utilized in order to provide a complete control circuit for all of the valves. The primary winding of the transformer I48 is connected to be energized in accordance with the potential appearing across the polyphase output circuit III. Each of the other valves corresponding to valve I42 includes one of the other secondary windings of the transformer I 48 and one of the current transformers I49, I50, I5I, I52 and I53. In order to start the apparatus each of the auxiliary valves is provided with a starting switch such as switch I54 which is momentarily closed in order to start the valve converting apparatus. As soon as the valves have been rendered conductive the switch is opened and the valves are then rendered conductive in accordance with the normal operation of the control circuit.

As the load increases on the output circuit III the current component flowing through the conductor to which the current transformer I41 is connected will increase so as to increase the voltage component supplied by this transformer to the control circuit of the valve I42 thus causing the valve to become conductive earlier with the result that the moment of ignition of the main valve is correspondingly advanced. It is believed that since the operation of the control circuit of this system is similar to the control circuit shown in preceding flgures'it will be unnecessary to set forth the detailed operation thereof. If the valve converting system is utilized as an asynchronous tie between two alternating current systems or as a converter between two alternating current systems of different frequencies, it will be apparent to those skilled in the art that the arrangement shown upon proper adjustment can be made to operate to transfer energy in the opposite direction.

While I have illustrated my invention as embodying an arrangement for transmitting energy from a three phase source of alternating current to a three phase alternating current motor or load circuit, it will beobvious to those skilled in the art that my invention is of general application to arrangements for transmitting energy from an alternating current supply circuit of any number of phases to an alternating current motor or circuit of any number of phases.

While I have described what I at present consider the preferred embodiments of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention, and I therefore aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The combination of a source of current, a load circuit, and an electric valve frequency converter interconnecting said source and said load circuit, said converter comprising a plurality of controlled electric valves, a control circuit for said valves including a source of potential connected in series with a plurality of controlled auxiliary valves, a control potential for said auxiliary valves, and means responsive to a plurality of electrical conditions of said load circuit for controlling the moment at which said control potential renders said auxiliary valves conductive.

2. In combination, a source of current, a polyphase alternating current load circuit, a plurality of controlled main electric valves for transmitting energy from said source to said load circuit,

a control circuit for said valve including a source of control potential, a distributor driven in accordance with the frequency of said alternating current load circuit, a plurality of controlled auxiliary valves, said control potential source, said distributor and said auxiliary valves being connected in series, and means for controlling the conductivity of said auxiliary valves in accordance with the current and voltage conditions of each of the conductors of the polyphase alternating current load circuit.

3. In combination, a source of alternating current, a polyphase alternating current load circuit, a plurality of controlled main electric valves for transmitting energy from said source to said load circuit, a control circuit for said valves including means for obtaining potential from said source and a plurality of auxiliary electric valves for controlling the application of said potential to said valves, a control circuit for said auxiliary valves including means for deriving a potential component proportional to the potential appearing across said load circuit, and means for deriving a potential component proportional to the current flowing through each of the conductors of said load circuit.

4. In combination, a source of alternating current, an alternating current load circuit, a plurality of controlled electric valves for transmitting energy from said source to said load circuit, a control circuit for said valves including means for obtaining a potential from said source and a plurality of auxiliary electric valves for controlling the application of said potential to said valves, and a control circuit for said auxiliary valves including a source of control potential, andmeans responsive to increasing load upon said load circuit to advance the moment at which said auxiliary valves are rendered conductive by said control potential.

5. In combination, an alternating current input circuit, an alternating current output circuit, a plurality of controlled main electric valves for transmitting energy between said circuits, a control circuit for said valves including a source of potential and a plurality of controlled auxiliary valves connected in series with said potential, and a control circuit for said auxiliary valves including means responsive to the frequency of said output circuit and means responsive to current and voltage conditions of said output circuit for controlling the conductivities of said auxiliary valves.

ALBERT H. MITIAG. 

